As a cutting tool used for applying cutting working to a workpiece made of metal or the like, there has been known a cutting tool described in WO 2009-157540 (patent document 1), a cutting tool described in JP 2006-263845 A (patent document 2) and a cutting tool described in JP 2010-179380 A (patent document 3). All these cutting tools described in these patent documents 1 to 3 are used in applying working to an inner dimeter of a workpiece having a cylindrical shape. Each cutting tool includes a holder, and a cutting insert (insert) mounted on a front end of the holder. Particularly, both cutting tools described in patent documents 2 and 3 are tools used in applying grooving process.
When a workpiece having a cylindrical shape includes a cylindrical bottom, chips flow toward a rear end side from a front end side of the cutting tool, and are discharged to the outside from an opening portion located at the rear end side of the workpiece having a cylindrical shape.
The larger an outer diameter of the holder, the higher the rigidity of the holder becomes. Accordingly, in applying inner diameter working, considered is the use of a holder which includes a large outer diameter so as to make the outer diameter of the holder set close to an inner diameter of the workpiece as much as possible. However, the larger the outer diameter of the holder becomes, the narrower a space between the holder and the workpiece becomes and hence, the space is liable to be clogged by chips. Particularly, in applying grooving process using the cutting tool described in patent documents 2 and 3, compared to the case where inner diameter working is applied using the cutting tool described in patent document 1, a width of chips easily becomes large and hence, the space is liable to be clogged by the chips.
In the holders of both cutting tools described in patent documents 2 and 3, when compared a first portion of the upper jaw portion which is located above an insert pocket and a second portion of the upper jaw portion which is located closer to a rear end side of the holder than the first portion to each other, an outer periphery of the second portion projects upward or sideward from the first portion. Accordingly, when the outer diameter of the holder is increased, in discharging chips through a space above the upper jaw portion, there is a possibility that a portion of the holder located closer to a rear end side than the upper jaw portion is clogged by the chips.
The present embodiment has been made in view of such drawbacks, and it is an object of the present embodiment to provide a holder which can discharge chips in a stable manner even in applying grooving process.